U.S. patent application number 10/775456 was filed with the patent office on 2004-10-14 for electro-optical module for transmitting and/or receiving optical signals of at least two optical data channels.
Invention is credited to Melchior, Lutz, Murphy, Thomas, Plickert, Volker, Weigert, Martin.
Application Number | 20040202478 10/775456 |
Document ID | / |
Family ID | 32797693 |
Filed Date | 2004-10-14 |
United States Patent
Application |
20040202478 |
Kind Code |
A1 |
Melchior, Lutz ; et
al. |
October 14, 2004 |
Electro-optical module for transmitting and/or receiving optical
signals of at least two optical data channels
Abstract
The invention relates to an electro-optical module for
transmitting and/or receiving optical signals of at least two
optical data channels which are guided in an optical waveguide. The
module includes at least one transmission component and at least
one reception component. According to the invention, the optical
waveguide is formed as a single waveguide piece with a bevelled end
face which has a wavelength-selective filter or is connected to
such a filter. Light from one data channel is reflected at the
wavelength-selective filter and coupled out at an angle to the
optical axis of the waveguide piece. Light of the other data
channel passes through the wavelength-selective filter and enters
the bevelled end face. A free beam region is formed between the
bevelled end face and the transmission and reception
components.
Inventors: |
Melchior, Lutz; (Berlin,
DE) ; Plickert, Volker; (Brieselang, DE) ;
Weigert, Martin; (Berlin, DE) ; Murphy, Thomas;
(Berlin, DE) |
Correspondence
Address: |
ESCHWEILER & ASSOCIATES, LLC
NATIONAL CITY BANK BUILDING
629 EUCLID AVE., SUITE 1210
CLEVELAND
OH
44114
US
|
Family ID: |
32797693 |
Appl. No.: |
10/775456 |
Filed: |
February 10, 2004 |
Current U.S.
Class: |
398/141 |
Current CPC
Class: |
G02B 6/421 20130101;
G02B 6/4215 20130101; G02B 6/4214 20130101; G02B 6/29361 20130101;
G02B 6/4246 20130101 |
Class at
Publication: |
398/141 |
International
Class: |
H04B 010/12 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 2003 |
DE |
103 07 763.4 |
Claims
1. An electro-optical module for transmitting or receiving optical
signals of at least two optical data channels, comprising: an
optical waveguide formed in the module as a single waveguide piece
with a bevelled end face that has a wavelength-selective filter
associated therewith; a transmission component emitting light that
is coupled into the optical waveguide; a reception component that
receives light coupled out from the optical waveguide, wherein
light of one data channel travels in the optical waveguide and is
reflected at the wavelength-selective filter and couples out to the
reception component at an angle to an optical axis of the waveguide
piece, wherein light of the other data channel from the
transmission component passes through the wavelength-selective
filter and enters the bevelled end face, and wherein a free beam
region is formed between the bevelled end face and the transmission
component and the reception component, respectively.
2. The module of claim 1, wherein the end face of the optical
waveguide is coated with a wavelength-selective filter, or a
separate carrier with a wavelength-selective filter is arranged on
the end face.
3. The module of claim 1, wherein the angle of the optical
waveguide end face to the optical axis of the waveguide piece is
substantially 60.degree..
4. The module of claim 1, wherein the optical axes of the
transmission and reception components run at an angle of other than
90.degree. relative to one another.
5. The module of claim 1, wherein the waveguide piece comprises a
glass ferrule in which the optical waveguide is located and which
is transparent to light of the wavelengths used.
6. The module of claim 1, wherein the transmission component and
the reception component are fastened on a common module housing and
are positioned thereon at a defined angle to one another.
7. The module of claim 6, wherein the transmission component and
the reception component are hermetically fixed in advance on the
module housing.
8. The module of claim 6, wherein the module housing comprises
defined stops for fastening the transmission component and the
reception component thereto in a hermetically tight fashion.
9. The module of claim 6, wherein the waveguide piece is
preassembled on an insertion part that is configured for insertion
into the module housing.
10. The module of claim 9, wherein the insertion part and the
waveguide piece are arranged in a hermetically tight fashion in the
module housing.
11. The module of claim 9, wherein the insertion part comprises a
flange via which the insertion part and the waveguide piece are
fastened in a defined arrangement in the module housing.
12. The module of claim 11, wherein the waveguide piece is
positioned in the module housing in such a way that light emitted
by the transmission component is focused onto the end face of the
waveguide piece.
13. The module of claim 1, wherein the transmission or reception
component is respectively arranged on a TO base plate that is
inserted into corresponding holding regions of the module
housing.
14. The module of claim 1, further comprising a lens provided in
the free beam region between the end face of the waveguide piece
and the transmission component or the reception component,
respectively.
15. The module of claim 14, wherein the lens is integrated into the
transmission component or the reception component.
16. The module of claim 6, wherein the waveguide piece projects in
a defined fashion from the module housing at its end opposite the
bevelled end face.
17. The module of claim 1, wherein the optical waveguide comprises
a single-mode waveguide.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of the priority date of
German application DE 103 07 763.4, filed on Feb. 14, 2003, the
contents of which are herein incorporated by reference in their
entirety.
FIELD OF THE INVENTION
[0002] The invention relates to an electro-optical module for
transmitting and/or receiving optical signals of at least two
optical data channels.
BACKGROUND OF THE INVENTION
[0003] An electro-optical module is disclosed in EP-A-238 977.
Separately encapsulated transmission and reception modules are
provided in TO design, and they are mutually adjusted, together
with a fibre pigtail, in a common housing and fastened. A free-beam
optics is implemented between the fibre pigtail and the
transmission and reception modules. A lens serves the purpose of
focusing the light beams which are coupled into or out of the fibre
pigtail. Moreover, for the purpose of wavelength separation a
wavelength-selective filter arranged in the free beam region is
provided which separates light emitted by the fibre end from the
beam path and feeds it to the reception module.
[0004] A disadvantage of this known module is a relatively complex
design owing to the use of a plurality of parts (lens, filter) in
the free beam region. These parts must be positioned with high
accuracy and, in the case of operation in a damp atmosphere, be
protected against instances of condensation which can occur.
[0005] WO-A-02/088812 discloses an optical arrangement in which
waveguide structures and wavelength-selective elements are formed
on a substrate, for example, using glass on silicon technology.
Transmission and reception modules are arranged on the substrate
surface. High costs for the substrate materials are disadvantageous
in the case of such arrangements.
[0006] WO-A-02/095470 describes an electro-optical module for
transmitting and/or receiving optical signals of at least two
optical data channels which are guided in an optical waveguide. The
optical waveguide forms in the module at least two optical
waveguide sections with in each case at least one bevelled end face
which is coated in a wavelength-selective fashion, the optical
waveguide sections being positioned axially one behind another at
the bevelled end faces. For an optical data channel, light is
coupled out from the optical waveguide, with light of the optical
data channel being reflected at the wavelength-selectively coated
end face and in this case being coupled out substantially
perpendicular to the optical axis of the waveguide section. The
waveguide sections are arranged in a mounting tube centring the
sections relative to one another.
[0007] Even though this known module requires no additional lenses,
and the optical waveguide is guided to the greatest possible extent
in the waveguide, there is the disadvantage, nevertheless, that the
mounting tubes centring the waveguide sections are relatively
expensive and complicated to produce.
SUMMARY OF THE INVENTION
[0008] It is the object of the present invention to make available
an optical module for transmitting and/or receiving optical signals
which is of simple and compact design, manages with few parts and
can be produced cost effectively.
[0009] Consequently, the invention is distinguished in that the
optical waveguide is formed in the module as a single waveguide
piece with a bevelled end face which has a wavelength-selective
filter or is connected to such a filter. In this case, firstly,
light of one data channel is reflected at the wavelength-selective
filter and coupled out or in at an angle to the optical axis of the
waveguide piece. Light of the other data channel passes through the
wavelength-selective filter and exits from or enters the bevelled
end face, light likewise being coupled out or in at an angle to the
optical axis of the waveguide piece. Formed between the bevelled
end face of the waveguide piece and the transmission component as
well as the reception component is a free beam region which is
traversed by the light coupled in or out on its way from the
transmission component or to the reception component.
[0010] The solution according to the invention envisages a design
concept in which only an optical waveguide section or a waveguide
piece is provided. The light signals of both data channels are
coupled into or out of the waveguide piece at the bevelled end face
of the waveguide piece. The angle of the bevelled end face is
dimensioned in such a way in this case that the light reflected at
the end face transirradiates the cladding of the waveguide piece
(and any adjacent materials) and is then emitted obliquely. The
other signal component passes through the end face of the waveguide
piece. This process automatically produces an angular arrangement
of transmission component and reception component.
[0011] The solution according to the invention is distinguished by
a particularly simple and cost effective design, since only one
waveguide section is provided and there is therefore no need to use
mounting tubes to position individual wave waveguide sections
relative to one another. Again, there is no need for any separate
beam splitter elements in the free beam region. Lenses which may be
present for beam shaping are preferably integrated in the
transmission and reception components, and so no separate parts
need be arranged and positioned in the free beam region.
[0012] It may be pointed out that the arrangement according to the
invention comprises both the use of a transmission component and a
reception component, and the use of two transmission components or
two reception components, light of two wavelengths being coupled
into or out of the wave guide piece in the latter case, that is to
say the module operates as a multiplexer or demultiplexer. It may
also be pointed out that in addition to the actual electro-optical
elements such as laser diode and reception diode, the terms of
transmission component and reception component also comprise, if
appropriate, assigned components such as beam shaping elements,
driver modules and monitor diodes. A transmission component or
reception component is preferably in each case a micromodule, known
per se, for generating or detecting signals.
[0013] The angle of the inclined end face of the waveguide piece
uniquely determines the relative position of transmission component
and reception component, and the direction of the optical beam axes
of these components. Thus, both the beam direction of the reflected
signal and the beam direction of the light beams entering or
exiting the end face are determined uniquely from the law of
reflection and the law of refraction.
[0014] In a preferred refinement of the invention, the angle of the
end face to the optical axis of the waveguide piece is
substantially 60.degree.. The optical axis of the component which
emits or receives the light reflected at the end face, is then
inclined at an angle of approximately 61.degree. to the optical
axis of the waveguide piece. The optical axis of the component that
emits or receives the light passing through the end face is
inclined at an angle of approximately 7.degree. to the optical axis
of the waveguide piece. The optical axes of the transmission and
reception components are therefore arranged at an angle of other
than 90.degree. relative to one another. This also holds for other
bevel angles of the end face, and so this feature can be regarded
as characteristic of the present invention.
[0015] In a preferred refinement of the invention, the waveguide
piece comprises a glass ferrule which is transparent to light of
the wavelengths used. At its ends, the glass ferrule preferably has
an end face bevelled in accordance with the optical waveguide such
that there is a plane termination. The reflected light firstly
transirradiates the cladding of the optical waveguide and then the
glass ferrule, or vice versa. The glass ferrule permits the optical
waveguide of the waveguide piece to be held and handled
securely.
[0016] Since the bevel of the end face of the waveguide piece fixes
the position of the transmission and reception components (or of
two transmission components or two reception components), given a
defined bevel of the end face the transmission component and the
reception component can be preassembled at a module housing. The
transmission component and the reception component are consequently
preferably fastened on a common module housing and positioned
thereon at a defined angle to one another.
[0017] The transmission component and the reception component are
preferably hermetically fixed in advance on the module housing and
so after the waveguide piece has also been introduced and fastened
in a hermetically tight fashion the housing interior is sealed in a
hermetically tight fashion from the outside.
[0018] The module housing preferably has defined stops for
fastening the transmission component and/or the reception component
in a hermetically tight fashion. This permits in a simple way a
precise positioning of the components on the module housing, and
also simple fastening.
[0019] In a preferred refinement, the waveguide piece is
preassembled on an insertion part which is inserted into the module
housing. The waveguide piece projects in this case with its
bevelled end face into the interior of the module housing. The
insertion part preferably has a flange via which the insertion part
and the waveguide piece can be fastened in a defined arrangement in
the module housing. The insertion part is preferably fastened on
the module housing by providing a hermetic seal. If, as preferred,
there is provision for the two components also to be fastened on
the housing in a hermetically tight fashion, the module interior is
hermetically sealed off from the outside. There is then
advantageously no need for the individual components of the
transmission component and reception component also to be of
hermetically tight design, as well.
[0020] In a preferred refinement, the waveguide piece is positioned
in the module housing in such a way that light emitted by the
transmission component is focused exactly onto the end face of the
waveguide piece. This can be done, for example, because of an
active adjustment process. The adjustment is preferably performed
with reference to the transmission component, since the reception
component generally has a larger receiving surface than the beam
aperture from the waveguide piece, and so tolerances are
compensated by the large receiving surface. It is therefore
preferred that the components of the transmission component focus
the light onto the waveguide piece, and that the reception
component has a receiving surface of sufficient size, or
alternatively a focusing optics.
[0021] Instead of an active adjustment, it is also entirely
possible in principle to conceive of a passive adjustment, the
position of the waveguide piece and the position of the end face
being fixed by the position in the insertion part and the position
of the latter on the housing.
[0022] The transmission and reception components are each
preferably arranged on a base plate, in particular a TO base plate
(TO header) which can be inserted in each case into a corresponding
holding region of the module housing. It is also possible in
principle for the transmission and reception components to be
arranged in a complete housing, for example a TO housing, which is
then inserted into the module housing.
[0023] A multiplicity of designs can be selected for the
transmission component and the reception component as well as for
the base plate or a housing. For example, instead of being arranged
on TO headers the transmission and reception components can be
arranged on lead frames or flexible wiring carriers. In addition to
edge-emitting lasers, it is also possible for vertically emitting
lasers (VCSELs), in particular, to be used as transmission
components, and these are then coupled directly into the waveguide
piece by means of a focusing optics.
[0024] The free beam region between the end face of the waveguide
piece and the transmission component or the reception component in
each case preferably has a lens which serves the purpose of beam
focusing. The lens is preferably integrated into the transmission
component or reception component such that the free beam region has
no separate elements which would have to be positioned.
[0025] The waveguide piece projects in a preferably defined fashion
from the module housing at its end opposite the bevelled end face.
This provides a coupling region for connecting a fibre plug, for
example. It is possible in principle for an optical fibre to be
connected in this case to the waveguide piece via any desired
optical connections.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention is explained in more detail below with
reference to the figures of the drawing and with the aid of an
exemplary embodiment. In the drawing:
[0027] FIG. 1 shows a first perspective view of an electro-optical
module for transmitting and receiving optical signals;
[0028] FIG. 2 shows a second perspective view of the module of FIG.
1;
[0029] FIG. 3 shows a view from below of the module of FIGS. 1 and
2, and
[0030] FIG. 4 shows a section through the module of FIGS. 1 to 3
along the line A-A of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The figures show an electro-optical module for transmitting
and receiving optical signals which are transmitted in an optical
waveguide (bidirectional transceiver). As illustrated in FIG. 4,
the module has a transmission component 1 designed as a micromodule
assembly with an optical axis 101, a reception component 2,
likewise designed as a micromodule assembly, with an optical axis
201, and a single-mode waveguide 300, arranged in a waveguide piece
3, with an optical axis 301. The transmission component 1, the
reception component 2 and the waveguide piece 3 are arranged in a
common, unipartite housing 5 and positioned relative to one another
thereon.
[0032] The transmission component 1 is arranged on a carrier 6
which is of TO design in the exemplary embodiment illustrated, but
can also be of other designs in principle. The transmission
component or the micromodule assembly 1 comprises a laser chip 102,
a monitor diode 103, a mirror surface 104 and a focusing lens 105.
The laser chip 102 is designed as an edge-emitting laser chip, the
light coupled out of the laser 102 being deflected at the mirror
surface 104 by 90.degree. and focused by the lens 105.
[0033] In order to fasten the carrier 6 on the housing 5, the said
carrier has a circumferential flange surface 601. The latter bears
against an assigned stop surface 501 of the module housing 5. Two
stop surfaces 501, 601 exhibit an angle of approximately 97.degree.
to the optical axis 301 of the waveguide piece 3.
[0034] The reception component 2 is likewise arranged on a carrier
7 of TO design. The corresponding micromodule assembly comprises a
carrier substrate 203, a reception diode 202 fastened thereon, and
a lens 205 fastened thereby on an intermediate carrier 204.
[0035] Just like the carrier 5 of the transmission component 1, the
carrier 7 of the reception component 2 has a circumferential flange
701 which corresponds to a corresponding stop surface 502 of the
housing 5. These stop surfaces 701, 502 are at an angle of
approximately 61.degree. to the optical axis 301 of the waveguide
piece 3.
[0036] The carriers 6, 7 of TO design each have, in a way known per
se, electrical bushings 602, 702 with the aid of which the
components 1, 2 are fed electric signals. The carriers 6, 7 are
hermetically fastened on the housing 5, for example by means of a
welding operation.
[0037] The above explanation of the transmission and reception
components 1, 2 is to be understood merely by way of example. In
principle, any desired arrangements of transmission and reception
components can be used. For example, the transmission module 1 can
have a vertically emitting laser diode. Again, instead of carriers
of TO design it is possible to use carriers with other designs.
[0038] The optical waveguide 300 is arranged in a glass ferrule
302. Together, they form the waveguide piece 3. The common end
faces 303, 304 of optical waveguide 300 and glass ferrule 302 each
run in parallel and are ground flat.
[0039] The optical waveguide 300 and the glass ferrule 302 are
located in an plug-in part 8 which forms a cylindrical part 81 and
a flange 82. The cylindrical part 81 serves to receive and hold the
waveguide piece 3. The flange 82 corresponds to stop surfaces 503
of the housing 5. This permits a hermetically tight fastening of
the plug-in part 8, and thus of the waveguide piece 3 in the
housing 5.
[0040] The cylindrical part 81 of the plug-in part 8 is inserted in
this case into a bore 504 in the housing 5. The diameter of the
cylindrical part 81 is smaller than the diameter of the bore 504,
and so an active adjustment in the x/y directions can be performed
before fastening the plug-in part 8, and thus the waveguide piece
3.
[0041] At its end averted from the housing 5, the waveguide piece 3
has a vertical end face 304 which provides an interface to an
optical-fibre cable to be fastened on the module. Such an optical
fibre cable is fastened on the end of the waveguide section 3 via
conventional optical plug-in connections.
[0042] The end face 303, formed in the housing interior, of the
waveguide piece 3 has a bevel of 60.degree. to the optical axis 301
of the waveguide piece 3 or the optical waveguide 300 in the
exemplary embodiment illustrated. A wavelength-selective filter 4
is applied to the end face 303. The filter 4 is applied using a
vacuum process, for example. Alternatively, a wavelength-selective
filter is applied to a separately produced filter plate which is
then fastened on the end face 303, for example bonded to it.
[0043] In order to position the end face 303 in the direction of
rotation about the optical axis 301, latching marks (not
illustrated separately), for example, are provided on the flange 82
of the plug-in part 8 and on the stop surface 503 of the housing 5,
the said markings corresponding to one another and providing
fastening in a specific angular position. In the exemplary
embodiment illustrated, the angular position is such that the
bevelled end face 303 runs perpendicular to the plane of the
drawing in FIG. 4.
[0044] In the exemplary embodiment illustrated, the
wavelength-selective filter 4 is transparent to light of a first
wavelength which is emitted by the transmission component 1. The
wavelength-selective filter 4 is, by contrast, reflecting to light
of a second wavelength, which is received by the reception
component 2. Consequently, the light which propagates in the
waveguide 300 in the direction of the bevelled end face 303 is
reflected at the wavelength-selective filter 4. Because of the
predetermined geometry, the reflected light firstly transirradiates
the cladding region of the optical waveguide 300, and then enters
the glass ferrule 302. After transirradiating the glass ferrule
302, it exits the latter and, after traversing a free beam region,
is focused onto the reception diode 202 by the lens 205 of the
reception component 2.
[0045] The reflected light therefore does not exit the end face of
the glass fibre 300, but is emitted to the outside through the
cladding and the adjoining glass ferrule 302. The optical axis 201
of the reception component runs at an angle of approximately
61.degree. to the axis 301 of the optical waveguide 2.
[0046] It may be pointed out that the end face 303 of the waveguide
piece 3 preferably has a bevel such that the light reflected at the
end face 303 transirradiates the glass ferrule 302 as vertically as
possible in order to keep as small as possible a beam deflection
owing to a refraction of light at the transition from ferrule to an
adjacent free beam region. The alignment at an angle of 60.degree.
to the optical axis 301 of the waveguide piece 3 is only one
example of a preferred inclined position of the end face.
[0047] In one development at least the free beam region between
ferrule 302 and reception component 2 is filled with an
index-matched potting material, in order to minimize a refraction
of light at the ferrule/free beam region transition.
[0048] Light emitted by the transmission component 1 is focused
exactly onto the end face of the optical waveguide 300 via the lens
105. Since the wavelength-selective filter 4 is transparent to the
wavelength of the transmission component 1, the light enters the
optical waveguide 300 through the end face 303 and propagates in
the optical waveguide 300 in the direction opposite to the light to
be detected.
[0049] It may be pointed out that the light likewise traverses a
free beam region between the transmission component 1 and the end
face 303 of the optical waveguide 300. The optical axis 101 of the
transmission component 1 runs at an angle of approximately
7.degree. to the optical axis 301 of the optical waveguide 300. The
optical axes 101, 201 of transmission component 1 and reception
component 2 thereby form an angle of other than 90.degree.. This
results in an arrangement typical of the module design
described.
[0050] The optoelectronic module is assembled by firstly fastening
the transmission component 1 and the reception component 2 with the
assigned carriers 6, 7 in a hermetically tight fashion on the
housing 5. Preassembly is possible, since the bevel of the end face
303 of the optical waveguide 100 defines the relative position of
transmission component 1 and reception component 2.
[0051] The waveguide piece 3 arranged in the plug-in part 8 is now
inserted into the housing 5. An active adjustment in the x/y
directions is performed by appropriately displacing the flange 82
on the stop surface 503 of the housing 5. The adjustment is carried
out in such a way that the maximum power of the transmission
component 1 is coupled into the optical waveguide 2.
[0052] The position of the end face 303 in the z-direction is fixed
by the length of the waveguide piece 3 in the plug-in part 8, in
particular the length of the part projecting from the cylindrical
region 81, and is preset. An adjustment with regard to the
rotational orientation with respect to the optical axis 301 is
performed, as mentioned above, by additional latching markings on
the flange 82 and the stop surface 503 of the housing 5, for
example.
[0053] It is important that the light emitted by the transmission
component 1 is focused onto the end face 303 of the optical
waveguide 2 during the adjustment. Design tolerances with regard to
the reception component 2 are tolerated by virtue of the fact that
the reception component 2 has a lens 205 which focuses the beam
onto a receiving surface 206 which is preferably larger than the
focusing spot of the light to be detected.
[0054] The invention is not restricted in its design to the
exemplary embodiment described above. For example, given a
fundamentally identical design, it is also possible to use two
transmission components or two reception components instead of one
transmission component and one reception component. Furthermore,
the angles used can differ, and the transmission and reception
components can be differently designed and be arranged on other
types of carriers or in housings. All that is important is that the
bevelled end face, provided with a wavelength-selective filter, of
an optical waveguide separates signals of two wavelengths, signals
of one wavelength passing through the end face, and the signals of
the other wavelength being reflected at the end face. The light
signals separated in this way propagate via a free beam region to a
receiving device, or are emitted by a transmitting device onto the
bevelled end face via a free beam region.
* * * * *